The present invention relates to a trailer fastening device. More particularly, the present invention relates to a trailer fastening device which has a spring to position a solid ball in a blind hole stably.
A conventional trailer fastening rod cannot fasten two trailer plates stably. When a road is uneven, the trailer plates will produce noise.
An object of the present invention is to provide a trailer fastening device which has a spring to position a solid ball in a blind hole stably.
Accordingly, a trailer fastening device comprises a fastening shaft, a collar, a spring, and a solid ball. The collar has a center hole, a through hole, and an inner recess hole receiving the spring and the solid ball. The fastening shaft has a middle blocking disk, a lower threaded rod disposed on a bottom of the middle blocking disk, and an upper rod disposed on a top portion of the middle blocking disk. The upper rod has a helical groove, a blind hole formed on an end of the helical groove, and the end of the helical groove being a bevel. The upper rod is inserted in the center hole of the collar. The collar is rotated until the solid ball reaches the blind hole of the upper rod along the helical groove of the upper rod.